Operando Raman spectroscopic evidence of electron-phonon interactions in NiO/TiO pn junction photodetectors

The pn junctions significantly affect the responsivity of photodetectors (PDs). However, the enhancement mechanism of the pn junction is still unclear. Herein, operando Raman spectroscopy was employed to study PDs with NiO/TiO 2 pn junctions composed of p-NiO nanoparticles (NPs) and n-TiO 2 nanotube arrays (TNAs). The results suggest that the built-in potential field of the NiO/TiO 2 interface decreases the charge transfer resistance and changes the vibrational frequency of the phonon modes of TiO 2 , which is attributed to the electron-phonon coupling effect. Operando Raman spectroscopy is proved to be a powerful tool for manufacturing highly responsive PDs. Operando Raman spectroscopy was used for noninvasive and nondestructive investigations of pn junctions in photodetectors under working conditions.